imcontour

Create contour plot of image data

Syntax

imcontour(I)

imcontour(I,levels)

imcontour(I,V)

imcontour(x,y,___)

imcontour(___,LineSpec)

[C,h] = imcontour(___)

Description

imcontour(I) draws a contour plot of the grayscale image I, choosing the number of levels and the values of levels automatically. imcontour automatically sets up the axes so their orientation and aspect ratio match the image.

imcontour(I,levels) specifies the number, levels, of equally spaced contour levels in the plot.

imcontour(I,V) draws contour lines at the data values specified in vector V. The number of contour levels is equal to length(V).

imcontour(x,y,___) uses the vectors x and y to specify the image x- and y coordinates.

imcontour(___,LineSpec) draws the contours using the line type and color specified by LineSpec. Marker symbols are ignored.

[C,h] = imcontour(___) returns the contour matrix, C, and the contour patches, h, that are drawn onto the current axes.

Examples

Create Contour Plot of Image Data

Read and display a grayscale image.

I = imread("rice.png");
imshow(I)

Create a contour plot of the image with three contour levels.

imcontour(I,3);

Input Arguments

I — Grayscale image

m-by-n matrix

Grayscale image, specified as an m-by-n matrix.

Data Types: single | double | int16 | uint8 | uint16 | logical

levels — Number of contour levels

numeric scalar

Number of contour levels, specified as a numeric scalar.

V — Value of contour levels

numeric vector

Value of contour levels, specified as a numeric vector with length greater than or equal to two. Use V = [v v] to compute a single contour at level v.

x — Image x values

2-element numeric vector | n-element numeric vector

Image x values, specified as one of the following:

• 2-element numeric vector of the form [xmin xmax] — Image extent in the x direction.

• n-element numeric vector — x-coordinate of each column.

y — Image y values

2-element numeric vector | m-element numeric vector

Image y values, specified as one of the following:

• 2-element numeric vector of the form [ymin ymax] — Image extent in the y direction.

• m-element numeric vector — y-coordinate of each row.

LineSpec — Line style and color

character vector | string scalar

Line style and color, specified as a character vector or string scalar containing a line style specifier, a color specifier, or both.

Example: "--r" specifies red dashed lines

These two tables list the line style and color options.

Line Style	Description	Resulting Line
"-"	Solid line
"--"	Dashed line
":"	Dotted line
"-."	Dash-dotted line

Color Specifier	Description	Appearance
r	red
g	green
b	blue
c	cyan
m	magenta
k	yellow
k	black
w	white

Output Arguments

C — Contour matrix

numeric matrix

Contour matrix, returned as a matrix with two rows. The matrix is defined according to the ContourMatrix property of the Contour object, h.

h — Contour patches

Contour object

Contour patches, returned as a Contour object.

Version History

Introduced before R2006a